| The experiments were carried out to study the effects of high temperature after anthesis on the structure of starch crystalline, starch grain morphology and different elements distribution in starch grains, to analyze the effects of high temperature after anthesis on starch characteristics and accumulation and relevant physiological mechanism in wheat growing in pots with temperature controlled and moisture controlled green house in different days after anthesis in Jiangsu Provincial Key Lab of Crop Genetics and Physiology from 2005 to 2007.The main results were as follows.1.The effects of heat stress after anthesis on the structure of starch crystalline.The structure of starch crystalline showed crystal A type under transient high temperature at different stages after anthesis, with a single peak at 15°and 23°respectively,a weak peak at 20°,conjoint bis peaks at 17°and 18°.Thus there was little influence of high temperature stress on the starch crystalline type. As for the degree of crystalinity,in 35℃and 40℃treatments, it was lower than that in CK with indistinctive difference and it descended with the postponing of treatment period. The results suggested that high temperature stress went against the formation of crystalline region in starch granule and it was more effective in anaphase. Starch crystal's peak values at 15°, 17°, and 18°were lower in 35℃and 40℃treatments than that in CK but the difference was not significant.Therefore,there were some influences of heat stress on the the formation of crystalline region in starch granule at maturity.2.The effects of heat stress after anhesis on the starch characteristics.Heat stress after anhesis had a significant impact on the starch characteristics in grains at maturity, including solubility, swelling power, peak viscosity, final viscosity and damaged starch. Solubility, swelling power and damaged starch were significantly increased in the treatment from 20th to 22th day after anthesis,which were higher than that in CK contrary to peak viscosity and final viscosity.It showed that starch traits were more sensitive to high temperature stress after anthesis in this period.Under the same temperature stress,it tended to rise, then fall with the postponing of treatment period except the 0th to 2th day treatments,while under the same treated stage, the stress effect of 40℃were more significant than 35℃.As for sedimentation values,it was higher than that in CK especially before the 25th day after anthesis in grains at maturity,which increased with the temperature climed in the same treated stage after the 10th day,while it descended with the postponing of treatment period in the same temperature.The 5th to 7th day, 40℃treatment was the highest.3. The effects of heat stress after anhesis on dynamics of grain starch accumulation amounts and starch content in grains at maturity.Under high temperature stress,the dynamics of grain starch accumulation showed"S"type curve change respectively.In 35℃treatments,amylose, amylopectin and starch accumulation amounts in grains declined significantly under heat stress at different stages after anthesis.The order of the treatments were CK>the 25th to 27th day>the 20th to 22th day>the 15th to 17th day>the 10th to 12th day>the 5th to 7th day after anthesis. Compared with CK, the ratio of amylose content to amylopectin content changed as"V"type and its lowest value were earlier under high temperature at the 13th day after anthesis.Moreover,the starch content and accumulation amounts in grains at maturity were lower than that in CK and its decrease amplitude falled with the postponing of treatment period while the 5th to 7th day, 40℃treatment was the lowest.4. The effects of heat stress after anhesis on chlorlphyll content and photosynthetic rate in flag leaves.The chlorlphyll content and photosynthetic rate descended obviously in 25℃and 35℃treatments, which were lower than that in CK and the stress effect of 35℃were more significant.The dynamics of photosynthetic rate in flag leaves ascended slightly first,then keeped dropping between the 5th to 10th day after the treatment in the 25th day after anthesis. However,the dynamics of chlorlphyll content in flag leaves showed that its descent range was little in the 6th day after the treatment in the 20th day after anthesis except the 0th to 2th day treatment contrary to after the 6th day after treatment.Moreover, after the 20th day after anthesis,it decreased rapidly after the treatment and then it was on the decline slowly.5.The effects of heat stress after anhesis on grain yield.Compared with CK, 1000 grain weight, grain yield per ear and grain yield per pot declined significantly under transient high temperature at different stages after anthesis at maturity,especially on the 20th day after anthesis and from the 5th to 7th day, 40℃treatment was the lowest.As for biomass per plant, the amount of transported dry matter accumulated before anthesis per plant, the amount of photosynthetic assimilation after anthesis per plant and economic coefficient,it was lower than that in CK respectively at different degree after heat stress particularly in the 20th day after anthesis.
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